There have been known methods for performing electrical measurement while scanning the surface of a sample with a probe having a small tip diameter in order to measure the electrical property of the minute region of the sample. Among them, a scanning probe microscope (SPM) which scans a sample surface with a probe of a nano order to measure the shape of the sample is widely used also in electric measurement.
A conductive probe used in the scanning probe microscope includes a cantilever having a conductive probe provided at a tip of the cantilever. The probe is scanned while the probe is pressed against the surface of a sample with a constant force, and a voltage is applied between the probe and the sample, to allow the electrical property measurement and mapping of the minute region to be performed.
The scanning probe microscope can evaluate local electrical property, but its spatial resolution is greatly affected by the tip radius of the probe. Since the conductive probe is normally made by vapor-depositing a conductive film such as a metal thin film on the surface of a shape measuring probe, the tip radius of the probe is at least about 20 nm. In order to obtain stable conductivity, the probe is covered with a conductive film made of Au, Pt, PtIr, or Rh having excellent oxidation resistance.
Since the tip of the probe is brought into contact with the surface of the sample whenever the electric resistance value of the sample is measured, the conductive film with which the probe is covered may be worn to cause impaired conductivity.
This requires a high spatial resolution which can be achieved in the measurement due to the conductive probe, and conductivity which can be maintained for a long time.